1. Field of the Invention
The present invention relates to a toner container that is removably mounted on an image forming apparatus for supplying toner consumed in image forming process, and the image forming apparatus.
2. Description of the Related Art
An electrophotographic image forming apparatus such as a copier, printer, facsimile, or multifunction product has been using a toner supply devise with a screw pump (a uniaxial eccentric screw pump or mohno pump) for delivering toner in a toner container to a developing device.
For example, Japanese Patent Application Laid-Open No. 2002-287497 discloses a toner supply devise. A bag-shaped toner container is removably mounted on an image forming apparatus, and connected to a tube (conveyor tube) via a nozzle. The tube has one end connected to a screw pump. The screw pump includes a rotor, a stator, a suction opening, a universal joint, and a motor. The rotor in the stator is rotatingly driven by the motor in a predetermined direction to cause a negative pressure (suction pressure) in the tube. Accordingly, toner is discharged from the toner container, and moves through the tube. The toner is sucked by the suction opening of the screw pump, sent into a space between the stator and the rotor, and is then carried to the other end side along the rotation of the rotor. The toner is discharged from an outlet of the screw pump, and supplied to a developing device.
The conventional toner supply device is formed of the toner container, the developing device, and the flexible tube serving as a toner supply path therebetween, and therefore, flexibility in layout of the entire image forming apparatus is increased. That is, the toner supply device with a screw pump conveys toner by generating pressure (negative pressure or positive pressure) in the flexible tube, which allows relatively free design of layout for the toner container, the developing device, and the toner supply path. Thus, the image forming apparatus can be downsized.
Besides, for example, Japanese Patent Application Laid-Open No. 2004-287404 discloses a cylindrical toner container with a spiral protrusion arranged on its inner surface. The toner container (toner bottle) replaceably mounted on a toner supply device of an image forming apparatus mainly includes a container portion and a held portion (cap). The container portion contains toner and includes a spiral protrusion on the inner surface. The container portion is rotatingly driven so that the toner is conveyed toward an opening thereof. The held portion is communicated with the opening and includes a toner outlet. The toner sent from the opening is discharged through the toner outlet. The toner is then supplied to a developing device via a toner conveyor pipe with a coil therein.
The conventional image forming apparatus, however, when used under a high-temperature and high-humidity environment, sometimes causes toner blocking in the tube (the tube is clogged with toner) due to a decrease in fluidity of toner moving through the tube (toner conveying ability). The toner blocking causes an insufficient toner supply to the developing device, and density on an output image is lowered. Additionally, such an insufficient supply of toner, which serves as a lubricant between the rotor and the stator of the screw pump, causes the stator to be worn out, leading to a failure in the toner supply device.